Charge transport materials for luminescent applications

ABSTRACT

There is provided a charge transport compound having Formula I: wherein: R1 through R5 are the same or different at each occurrence and can be hydrogen, alkyl, aryl, halogen, hydroxyl, aryloxy, alkoxy, alkenyl, alkynyl, amino, alkylthio, phosphino, silyl, —COR, —COOR, —PO3R2, —OPO3R2, or CN; R6 can be hydrogen, alkyl, aryl, alkylaryl, and arylalkyl; R is the same or different at each occurrence and can be hydrogen, alkyl, aryl, alkenyl, and alkynyl; and n is an integer from 0-3.

RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(e) fromProvisional Application No. 61/015,815 filed on Dec. 21, 2007 which isincorporated by reference in its entirety.

BACKGROUND INFORMATION

1. Field of the Disclosure

This disclosure relates in general to charge transport materials thatcan be used in luminescent applications. In particular, the materialscan be used as hosts for light-emitting materials. The disclosurefurther relates to electronic devices having at least one active layercomprising such a charge transport material.

2. Description of the Related Art

In organic photoactive electronic devices, such as organic lightemitting diodes (“OLED”), that make up OLED displays, the organic activelayer is sandwiched between two electrical contact layers in an OLEDdisplay. In an OLED, the organic photoactive layer emits light throughthe light-transmitting electrical contact layer upon application of avoltage across the electrical contact layers.

It is well known to use organic electroluminescent compounds as theactive component in light-emitting diodes. Simple organic molecules,conjugated polymers, and organometallic complexes have been used.Devices that use photoactive materials frequently include one or morecharge transport layers, which are positioned between a photoactive(e.g., light-emitting) layer and a contact layer (hole-injecting contactlayer). A device can contain two or more contact layers. A holetransport layer can be positioned between the photoactive layer and thehole-injecting contact layer. The hole-injecting contact layer may alsobe called the anode. An electron transport layer can be positionedbetween the photoactive layer and the electron-injecting contact layer.The electron-injecting contact layer may also be called the cathode.Charge transport materials can also be used as hosts in combination withthe photoactive materials.

There is a continuing need for charge transport materials for use inelectronic devices.

SUMMARY OF THE DISCLOSURE

There is provided a compound having Formula I:

wherein:

-   -   R¹ through R⁵ are the same or different at each occurrence and        are independently selected from the group consisting of        hydrogen, alkyl, aryl, halogen, hydroxyl, aryloxy, alkoxy,        alkenyl, alkynyl, amino, alkylthio, phosphino, silyl, —COR,        —COOR, —PO₃R₂, —OPO₃R₂, and CN;    -   R⁶ is selected from the group consisting of hydrogen, alkyl,        aryl, alkylaryl, and arylalkyl;    -   R is the same or different at each occurrence and is        independently selected from the group consisting of hydrogen,        alkyl, aryl, alkenyl, and alkynyl; and    -   n is an integer from 0-3.

There is also provided an electronic device comprising at least onelayer comprising the above compound.

The foregoing general description and the following detailed descriptionare exemplary and explanatory only and are not restrictive of theinvention, as defined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated in the accompanying figures to improveunderstanding of concepts as presented herein.

FIG. 1 includes an illustration of one example of an organic electronicdevice.

Skilled artisans appreciate that objects in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.For example, the dimensions of some of the objects in the figures may beexaggerated relative to other objects to help to improve understandingof embodiments.

DETAILED DESCRIPTION

Many aspects and embodiments are described herein and are merelyexemplary and not limiting. After reading this specification, skilledartisans will appreciate that other aspects and embodiments are possiblewithout departing from the scope of the invention.

Other features and benefits of any one or more of the embodiments willbe apparent from the following detailed description, and from theclaims. The detailed description first addresses Definitions andClarification of Terms followed by the Charge Transport Materials, theElectronic Device, and finally Examples.

1. Definitions and Clarification of Terms

Before addressing details of embodiments described below, some terms aredefined or clarified.

The phrase “adjacent to,” when used to refer to layers in a device, doesnot necessarily mean that one layer is immediately next to anotherlayer. On the other hand, the phrase “adjacent R groups,” is used torefer to R groups that are next to each other in a chemical formula(i.e., R groups that are on atoms joined by a bond).

The term “alkenyl” is intended to mean a group derived from an aliphatichydrocarbon having at least one carbon-carbon double bond. The term isintended to include heteroalkyl groups.

The term “alkoxy” is intended to mean a group having the formula —OR,which is attached via the oxygen, where R is an alkyl.

The term “alkyl” is intended to mean a group derived from an aliphatichydrocarbon having one point of attachment, and includes a linear, abranched, or a cyclic group. The term is intended to includeheteroalkyls. The term “alkylene” is intended to mean a group derivedfrom an aliphatic hydrocarbon and having two or more points ofattachment. In some embodiments, an alkyl group has from 1-20 carbonatoms. In some embodiments, the heteroalkyl groups have from 1-20 carbonatoms and from 1-5 heteroatoms.

The term “alkylthio” is intended to mean a group having the formula —SR,which is attached via the sulfur, where R is an alkyl.

The term “alkynyl” is intended to mean a group derived from an aliphatichydrocarbon having at least one carbon-carbon triple bond.

The term “aryl” is intended to mean a group derived from an aromatichydrocarbon having one point of attachment. The term is intended toinclude heteroaryls. The term “arylene” is intended to mean a groupderived from an aromatic hydrocarbon having two points of attachment. Insome embodiments, an aryl group has from 3-60 carbon atoms.

The term “blue” refers to radiation that has an emission maximum at awavelength in a range of approximately 400-500 nm.

The term “charge transport,” when referring to a layer, material,member, or structure is intended to mean such layer, material, member,or structure facilitates migration of such charge through the thicknessof such layer, material, member, or structure with relative efficiencyand small loss of charge. Hole transport materials facilitate positivecharge; electron transport material facilitate negative charge. Althoughlight-emitting materials may also have some charge transport properties,the term “charge transport layer, material, member, or structure” is notintended to include a layer, material, member, or structure whoseprimary function is light emission.

The prefix “fluoro” indicates that one or more hydrogen atoms have beenreplaced with a fluorine atom.

The prefix “hetero” indicates that one or more carbon atoms have beenreplaced with a different atom. In some embodiments, the different atomis N, O, or S.

The term “layer” is used interchangeably with the term “film” and refersto a coating covering a desired area. The term is not limited by size.The area can be as large as an entire device or as small as a specificfunctional area such as the actual visual display, or as small as asingle sub-pixel. Layers and films can be formed by any conventionaldeposition technique, including vapor deposition, liquid deposition(continuous and discontinuous techniques), and thermal transfer.Continuous deposition techniques, include but are not limited to, spincoating, gravure coating, curtain coating, dip coating, slot-diecoating, spray coating, and continuous nozzle coating. Discontinuousdeposition techniques include, but are not limited to, ink jet printing,gravure printing, and screen printing.

The term “organic electronic device,” or sometimes just “electronicdevice,” is intended to mean a device including one or more organicsemiconductor layers or materials.

Unless otherwise indicated, all groups can be substituted orunsubstituted. An optionally substituted group, such as, but not limitedto, alkyl or aryl, may be substituted with one or more substituentswhich may be the same or different. Suitable substituents include alkyl,aryl, nitro, cyano, —N(R⁷)(R⁸), halo, hydroxy, carboxy, alkenyl,alkynyl, cycloalkyl, heteroaryl, alkoxy, aryloxy, heteroaryloxy,alkoxycarbonyl, perfluoroalkyl, perfluoroalkoxy, arylalkyl, thioalkoxy,—S(O)₂—N(R′)(R″), —C(═O)—N(R′)(R″), (R′)(R″)N-alkyl,(R′)(R″)N-alkoxyalkyl, (R′)(R″)N-alkylaryloxyalkyl, —S(O)_(s)-aryl(where s=0-2) or —S(O)_(s)-heteroaryl (where s=0-2). Each R′ and R″ isindependently an optionally substituted alkyl, cycloalkyl, or arylgroup. R′ and R″, together with the nitrogen atom to which they arebound, can form a ring system in certain embodiments.

The term “photoactive” is intended to mean to any material that exhibitselectroluminescence or photosensitivity.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

Also, use of “a” or “an” are employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one or at least one and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

Group numbers corresponding to columns within the Periodic Table of theelements use the “New Notation” convention as seen in the CRC Handbookof Chemistry and Physics, 81^(st) Edition (2000-2001).

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of embodiments of the present invention, suitablemethods and materials are described below. All publications, patentapplications, patents, and other references mentioned herein areincorporated by reference in their entirety, unless a particular passageis cited. In case of conflict, the present specification, includingdefinitions, will control. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

To the extent not described herein, many details regarding specificmaterials, processing acts, and circuits are conventional and may befound in textbooks and other sources within the organic light-emittingdiode display, photodetector, photovoltaic, and semiconductive memberarts.

2. Charge Transport Materials

The new compounds described herein are particularly useful as hostmaterials for photoactive materials. The compounds have Formula I:

wherein:

-   -   R¹ through R⁵ are the same or different at each occurrence and        are independently selected from the group consisting of        hydrogen, alkyl, aryl, halogen, hydroxyl, aryloxy, alkoxy,        alkenyl, alkynyl, amino, alkylthio, phosphino, silyl, —COR,        —COOR, —PO₃R₂, —OPO₃R₂, and CN;    -   R⁶ is selected from the group consisting of hydrogen, alkyl,        aryl, alkylaryl, and arylalkyl;    -   R is the same or different at each occurrence and is        independently selected from the group consisting of hydrogen,        alkyl, aryl, alkenyl, and alkynyl; and    -   n is an integer from 0-3.

In Formula I, R¹, R³, R⁴, and R⁵ can represent one or more substituentswhich can be the same or different. In some embodiments, R¹, R³, R⁴, andR⁵ are independently selected from hydrogen, alkyl, alkoxy, and aryl. Insome embodiments, R¹, R³, R⁴, and R⁵ are all hydrogen.

In some embodiments, R² is an aryl group. In some embodiments, R² isselected from phenyl and naphthyl.

In some embodiments, R⁶ is selected from the group consisting of alkyl,aryl, alkoxyl, and aryloxy. In some embodiments, R⁶ is aryl. In someembodiments, R⁶ is selected from phenyl and naphthyl. In someembodiments, R⁶ is arylalkyl. In some embodiments, R⁶ is alkyl. In someembodiments, R⁶ is a branched alkyl.

In some embodiments, n is 0 or 1.

In some embodiments, the charge transport compound is selected fromCompounds H1 through H5 below.

The new charge transport compounds can be prepared by known coupling andsubstitution reactions. One general synthetic route is shown below.

The synthesis is exemplified further in the examples.

The new compounds described herein can be formed into films using liquiddeposition techniques.

3. Electronic Device

The present invention also relates to an electronic device comprising atleast one photoactive layer positioned between two electrical contactlayers, wherein the at least one layer of the device includes the newcharge transport compound described herein.

Organic electronic devices that may benefit from having one or morelayers comprising the new charge transport materials described hereininclude, but are not limited to, (1) devices that convert electricalenergy into radiation (e.g., a light-emitting diode, light emittingdiode display, or diode laser), (2) devices that detect signals throughelectronics processes (e.g., photodetectors, photoconductive cells,photoresistors, photoswitches, phototransistors, phototubes, IRdetectors), (3) devices that convert radiation into electrical energy,(e.g., a photovoltaic device or solar cell), and (4) devices thatinclude one or more electronic components that include one or moreorganic semi-conductor layers (e.g., a transistor or diode).

One illustration of an organic electronic device structure is shown inFIG. 1. The device 100 has a first electrical contact layer, an anodelayer 110 and a second electrical contact layer, a cathode layer 160,and a photoactive layer 140 between them. Adjacent to the anode is abuffer layer 120. Adjacent to the buffer layer is a hole transport layer130, comprising hole transport material. Adjacent to the cathode may bean electron transport layer 150, comprising an electron transportmaterial. As an option, devices may use one or more additional holeinjection or hole transport layers (not shown) next to the anode 110and/or one or more additional electron injection or electron transportlayers (not shown) next to the cathode 160.

Layers 120 through 150 are individually and collectively referred to asthe active layers.

In one embodiment, the different layers have the following range ofthicknesses: anode 110, 500-5000 Å, in one embodiment 1000-2000 Å;buffer layer 120, 50-2000 Å, in one embodiment 200-1000 Å; holetransport layer 130, 50-2000 Å, in one embodiment 200-1000 Å;photoactive layer 140, 10-2000 Å, in one embodiment 100-1000 Å; layer150, 50-2000 Å, in one embodiment 100-1000 Å; cathode 160, 200-10000 Å,in one embodiment 300-5000 Å. The location of the electron-holerecombination zone in the device, and thus the emission spectrum of thedevice, can be affected by the relative thickness of each layer. Thedesired ratio of layer thicknesses will depend on the exact nature ofthe materials used.

Depending upon the application of the device 100, the photoactive layer140 can be a light-emitting layer that is activated by an appliedvoltage (such as in a light-emitting diode or light-emittingelectrochemical cell), or a layer of material that responds to radiantenergy and generates a signal with or without an applied bias voltage(such as in a photodetector). Examples of photodetectors includephotoconductive cells, photoresistors, photoswitches, phototransistors,and phototubes, and photovoltaic cells, as these terms are described inMarkus, John, Electronics and Nucleonics Dictionary, 470 and 476(McGraw-Hill, Inc. 1966).

The charge transport compounds described herein can be present in thephotoactive layer or in a charge transport layer.

a. Photoactive Layer

The charge transport compounds described herein are useful as hosts forthe photoactive materials in layer 140.

The photoactive material can be any electroluminescent (“EL”) materialhaving the desired color. Electroluminescent materials include smallmolecule organic fluorescent compounds, fluorescent and phosphorescentmetal complexes, conjugated polymers, and mixtures thereof. Examples offluorescent compounds include, but are not limited to, pyrene, perylene,rubrene, coumarin, derivatives thereof, and mixtures thereof. Examplesof metal complexes include, but are not limited to, metal chelatedoxinoid compounds, such as tris(8-hydroxyquinolato)aluminum (Alq3);cyclometalated iridium and platinum electroluminescent compounds, suchas complexes of iridium with phenylpyridine, phenylquinoline, orphenylpyrimidine ligands as disclosed in Petrov et al., U.S. Pat. No.6,670,645 and Published PCT Applications WO 03/063555 and WO2004/016710, and organometallic complexes described in, for example,Published PCT Applications WO 03/008424, WO 03/091688, and WO 03/040257,and mixtures thereof. Electroluminescent emissive layers comprising acharge carrying host material and a metal complex have been described byThompson et al., in U.S. Pat. No. 6,303,238, and by Burrows and Thompsonin published PCT applications WO 00/70655 and WO 01/41512. Examples ofconjugated polymers include, but are not limited topoly(phenylenevinylenes), polyfluorenes, poly(spirobifluorenes),polythiophenes, poly(p-phenylenes), copolymers thereof, and mixturesthereof.

In some embodiments, the EL material is a cyclometalated complex ofiridium. In some embodiments, the complex has two ligands selected fromphenylpyridines, phenylquinolines, and phenylisoquinolines, and a thirdligand with is a β-dienolate. The ligands may be unsubstituted orsubstituted with F, D, alkyl, CN, or aryl groups.

In some embodiments, the EL material is selected from the groupconsisting of a non-polymeric spirobifluorene compound and afluoranthene compound.

In some embodiments, the EL material is a compound having aryl aminegroups. In one embodiment, the EL material is selected from the formulaebelow:

where:

A is the same or different at each occurrence and is an aromatic grouphaving from 3-60 carbon atoms;

Q is a single bond or an aromatic group having from 3-60 carbon atoms;

n and m are independently an integer from 1-6.

In one embodiment of the above formula, at least one of A and Q in eachformula has at least three condensed rings. In one embodiment, m and nare equal to 1. In one embodiment, Q is a styryl or styrylphenyl group.

In some embodiments, Q is an aromatic group having at least twocondensed rings. In some embodiments, Q is selected from the groupconsisting of naphthalene, anthracene, chrysene, pyrene, tetracene,xanthene, perylene, coumarin, rhodamine, quinacridone, and rubrene. Insome embodiments, A is selected from the group consisting of phenyl,tolyl, naphthyl, and anthracenyl groups.

In one embodiment, the EL material has the formula below:

where:

Y is the same or different at each occurrence and is an aromatic grouphaving 3-60 carbon atoms;

Q′ is an aromatic group, a divalent triphenylamine residue group, or asingle bond.

In some embodiments, the EL material is an aryl acene. In someembodiments, the EL material is a non-symmetrical aryl acene.

In some embodiments, the EL material is a chrysene derivative. The term“chrysene” is intended to mean 1,2-benzophenanthrene. In someembodiments, the EL material is a chrysene having aryl substituents. Insome embodiments, the EL material is a chrysene having arylaminosubstituents. In some embodiments, the EL material is a chrysene havingtwo different arylamino substituents.

In some embodiments, the EL material has blue or green emission.

In some embodiments, the ratio of host material to EL material is in therange of 5:1 to 20:1; in some embodiments, 10:1 to 15:1.

The new charge transport compounds described herein are particularlyuseful as hosts for fluorescent organic compounds, including aromaticand arylamino-aromatic compounds.

b. Other Device Layers

The other layers in the device can be made of any materials that areknown to be useful in such layers.

The anode 110, is an electrode that is particularly efficient forinjecting positive charge carriers. It can be made of, for example,materials containing a metal, mixed metal, alloy, metal oxide ormixed-metal oxide, or it can be a conducting polymer, or mixturesthereof. Suitable metals include the Group 11 metals, the metals inGroups 4-6, and the Group 8-10 transition metals. If the anode is to belight-transmitting, mixed-metal oxides of Groups 12, 13 and 14 metals,such as indium-tin-oxide, are generally used. The anode 110 can alsocomprise an organic material such as polyaniline as described in“Flexible light-emitting diodes made from soluble conducting polymer,”Nature vol. 357, pp 477-479 (11 Jun. 1992). At least one of the anodeand cathode is desirably at least partially transparent to allow thegenerated light to be observed.

The buffer layer 120 comprises buffer material and may have one or morefunctions in an organic electronic device, including but not limited to,planarization of the underlying layer, charge transport and/or chargeinjection properties, scavenging of impurities such as oxygen or metalions, and other aspects to facilitate or to improve the performance ofthe organic electronic device. Buffer materials may be polymers,oligomers, or small molecules. They may be vapour deposited or depositedfrom liquids which may be in the form of solutions, dispersions,suspensions, emulsions, colloidal mixtures, or other compositions.

The buffer layer can be formed with polymeric materials, such aspolyaniline (PANI) or polyethylenedioxythiophene (PEDOT), which areoften doped with protonic acids. The protonic acids can be, for example,poly(styrenesulfonic acid), poly(2-acrylamido-2-methyl-1-propanesulfonicacid), and the like.

The buffer layer can comprise charge transfer compounds, and the like,such as copper phthalocyanine and thetetrathiafulvalene-tetracyanoquinodimethane system (TTF-TCNQ).

In some embodiments, the buffer layer comprises at least oneelectrically conductive polymer and at least one fluorinated acidpolymer. Such materials have been described in, for example, publishedU.S. patent applications 2004-0102577, 2004-0127637, and 2005/205860

The compounds described herein can also be used as hole transportmaterials in hole transport layer 130. Examples of other hole transportmaterials for layer 130 have been summarized for example, in Kirk-OthmerEncyclopedia of Chemical Technology, Fourth Edition, Vol. 18, p.837-860, 1996, by Y. Wang. Both hole transporting molecules and polymerscan be used. Commonly used hole transporting molecules are:N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC),N,N′-bis(4-methylphenyl)-N,N′-bis(4-ethylphenyl)-[1,1′-(3,3′-dimethyl)biphenyl]-4,4′-diamine(ETPD), tetrakis-(3-methylphenyl)-N,N,N′,N′-2,5-phenylenediamine (PDA),a-phenyl-4-N,N-diphenylaminostyrene (TPS), p-(diethylamino)benzaldehydediphenylhydrazone (DEH), triphenylamine (TPA),bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)methane (MPMP),1-phenyl-3-[p-(diethylamino)styryl]-5-[p-(diethylamino)phenyl]pyrazoline(PPR or DEASP), 1,2-trans-bis(9H-carbazol-9-yl)cyclobutane (DCZB),N,N,N′,N′-tetrakis(4-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TTB),N,N′-bis(naphthalen-1-yl)-N,N′-bis-(phenyl)benzidine (α-NPB), andporphyrinic compounds, such as copper phthalocyanine. Commonly used holetransporting polymers are polyvinylcarbazole, (phenylmethyl)-polysilane,and polyaniline. It is also possible to obtain hole transportingpolymers by doping hole transporting molecules such as those mentionedabove into polymers such as polystyrene and polycarbonate. In somecases, a polymer of triarylamine is used, particularly a copolymer oftriarylamine and fluorene. In some cases the polymer or copolymer iscrosslinkable.

Examples of electron transport materials which can be used in layer 150include metal chelated oxinoid compounds, such astris(8-hydroxyquinolato)aluminum (Alq₃);bis(2-methyl-8-quinolinolato)(para-phenyl-phenolato)aluminum(III)(BAIQ); and azole compounds such as2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD) and3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (TAZ), and1,3,5-tri(phenyl-2-benzimidazole)benzene (TPBI); quinoxaline derivativessuch as 2,3-bis(4-fluorophenyl)quinoxaline; phenanthroline derivativessuch as 9,10-diphenylphenanthroline (DPA) and2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (DDPA); and mixturesthereof. Layer 150 can function both to facilitate electron transport,and also serve as a buffer layer or confinement layer to preventquenching of the exciton at layer interfaces. Preferably, this layerpromotes electron mobility and reduces exciton quenching.

The cathode 160, is an electrode that is particularly efficient forinjecting electrons or negative charge carriers. The cathode can be anymetal or nonmetal having a lower work function than the anode. Materialsfor the cathode can be selected from alkali metals of Group 1 (e.g., Li,Cs), the Group 2 (alkaline earth) metals, the Group 12 metals, includingthe rare earth elements and lanthanides, and the actinides. Materialssuch as aluminum, indium, calcium, barium, samarium and magnesium, aswell as combinations, can be used. Li-containing organometalliccompounds, LiF, and Li₂O can also be deposited between the organic layerand the cathode layer to lower the operating voltage.

It is known to have other layers in organic electronic devices. Forexample, there can be a layer (not shown) between the anode 110 andbuffer layer 120 to control the amount of positive charge injectedand/or to provide band-gap matching of the layers, or to function as aprotective layer. Layers that are known in the art can be used, such ascopper phthalocyanine, silicon oxy-nitride, fluorocarbons, silanes, oran ultra-thin layer of a metal, such as Pt. Alternatively, some or allof anode layer 110, active layers 120, 130, 140, and 150, or cathodelayer 160, can be surface-treated to increase charge carrier transportefficiency. The choice of materials for each of the component layers ispreferably determined by balancing the positive and negative charges inthe emitter layer to provide a device with high electroluminescenceefficiency.

It is understood that each functional layer can be made up of more thanone layer.

The device can be prepared by a variety of techniques, includingsequential vapor deposition of the individual layers on a suitablesubstrate. Substrates such as glass, plastics, and metals can be used.Conventional vapor deposition techniques can be used, such as thermalevaporation, chemical vapor deposition, and the like. Alternatively, theorganic layers can be applied from solutions or dispersions in suitablesolvents, using conventional coating or printing techniques, includingbut not limited to spin-coating, dip-coating, roll-to-roll techniques,ink-jet printing, screen-printing, gravure printing and the like. Thenew charge transport compounds described herein are particularly suitedto liquid deposition processes for forming films.

Devices frequently have additional hole transport and electron transportlayers.

It is understood that the efficiency of devices made with the compoundshaving Formula I described herein, can be further improved by optimizingthe other layers in the device. For example, more efficient cathodessuch as Ca, Ba or LiF can be used. Shaped substrates and novel holetransport materials that result in a reduction in operating voltage orincrease quantum efficiency are also applicable. Additional layers canalso be added to tailor the energy levels of the various layers andfacilitate electroluminescence.

The concepts described herein will be further described in the followingexamples, which do not limit the scope of the invention described in theclaims.

EXAMPLES Example 1

This example illustrates the preparation of charge transport materialCompound H1.

a. Preparation of Anthracene-9-triflate, Intermediate B

In a 1 L flask was added anthrone (compound A, 54 g, 275.2 mmol) in 1.5L dry methylene chloride. The flask was cooled in an ice bath and 83.7mL DBU (559.7 mmol) was added dropwise over 1.5 hours under N₂. Thesolution turned orange, became opaque, then turned deep red. To thestill cooled solution was added 58 mL trifluoromethanesulfonic anhydride(345 mmol) via syringe over about 1.5 hr by keeping the temperature ofthe solution below 5° C. When the reaction was almost complete after 3hrs, 1 mL additional trifluoromethanesulfonic anhydride was added andthe mixture was stirred for another 30 min. 500 mL of water was addedand the layers were separated. The aqueous layer was washed with DCM(3×200 mL) and the combined organic layer was dried over magnesiumsulfate, and then concentrated under reduced pressure to give a red oil.This red oil was passed through a silica gel (column solvent: hexane,then Hex/DCM=95/5) to provide a solid material. This material wasrecrystallized from hexane to yield 57.5 g (65%) of B as a whitecrystalline solid.

b. Preparation of 9-(Naphthalen-2-yl)-anthracene, Intermediate C

3 g of compound B (1 eq), 1.9 g of naphthalene-2-yl-boronic acid (1.2eq), 8.8 g of potassium phosphate tribasic (4.5 eq), 0.103 g ofpalladium (II) acetate (0.05 eq), and 0.129 g of tricyclohexylphosphine(0.05 eq) were combined in a 200 ml RB flask in the glove box, followedby the addition of 25 ml of toluene and 25 ml degassed water. Theresultant mixture was refluxed for 20 hrs under N₂. After cooling themixture to rt, the organic layer was separated and the aqueous layer wasextracted with DCM (3×50 ml). The combined organic layer was washed with100 ml brine, dried with MgSO₄, and concentrated under reduced pressureto a tan powder. By neutral alumina column chromatography using DCM asan eluent, 2.0 g of compound C (72%) was obtained as a solid.

c. Preparation of Intermediate D

9-(Naphthalen-2-yl)-anthracene, compound C, (30 g, 98.56 mmol) wassuspended in 300 mL DCM, followed by the addition of NBS (18.4 g, 103.38mmol) to the flask. The mixture was refluxed under N₂ by illuminatingthe reaction flask with 100 W lamp. After 1.5 h the reaction mixture wasconcentrated to the half of the total volume, then hot acetonitrile wasadded. The solution was allowed to cool to give a pale yellow solid. Thecrystal was filtered and washed with acetonitrile, providing 28.9 g ofcompound D (80%).

d. Preparation of Intermediate E

Into a solution of 9-bromo-10-naphthalen-2-yl-anthracene (compound D,12.0 g, 1 eq) dissolved in anhydrous THF (200 mL), was added slowlyn-BuLi (2.5 M in hexane, 12.4 mL, 1.2 eq) at −78° C. under N₂. The deepred reaction mixture was stirred for 2 hr. Triisopropylborate (5.89 g,1.2 eq) was added dropwise into the cooled solution and stirred at thistemperature for 0.5 h. The solution became bright yellow over this time.The reaction was warmed up to room temperature and stirred for 1 hr.After quenching the mixture with 20% HCl solution (100 mL) for 1 hr theorganic layer was separated and the aqueous layer was extracted withEtOAc (3×100 mL). The combined organic layer was dried over anhydroussodium sulfate, then concentrated under reduced pressure to a yellowsolid. This solid was suspended in a small amount of EtOAc and theprecipitated solid was filtered to give 7.8 g of compound E (72%).

e. Preparation of Compound H1

To the solution of 3-iodo-1-phenylindazole (1.1 g, 1 eq) in toluene (30mL) and ethanol (15 mL) were added 10-(2-naphthyl)-anthracene-9-boronicacid (compound E, 1.43 g, 1.2 eq), Pd(PPh₃)₄ (0.2 g, 0.05 eq), andNa₂CO₃ (2.18 g, 6 eq), followed by the addition of 25 ml of degassedwater. The mixture was refluxed overnight under N₂, and then it wasextracted with EtOAc (2×50 ml). The combined organic layer was washedwith water, dried with Na₂SO₄, and concentrated under reduced pressure.By silica gel column chromatography (20% DCM/hexane, then 10%EtOAc/hexane) compound H1 (1.29 g, 76%) was obtained as a pale yellowsolid.

Note that not all of the activities described above in the generaldescription or the examples are required, that a portion of a specificactivity may not be required, and that one or more further activitiesmay be performed in addition to those described. Still further, theorder in which activities are listed are not necessarily the order inwhich they are performed.

In the foregoing specification, the concepts have been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope ofinvention.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all the claims.

The use of numerical values in the various ranges specified herein isstated as approximations as though the minimum and maximum values withinthe stated ranges were both being preceded by the word “about.” In thismanner slight variations above and below the stated ranges can be usedto achieve substantially the same results as values within the ranges.Also, the disclosure of these ranges is intended as a continuous rangeincluding every value between the minimum and maximum average valuesincluding fractional values that can result when some of components ofone value are mixed with those of different value. Moreover, whenbroader and narrower ranges are disclosed, it is within thecontemplation of this invention to match a minimum value from one rangewith a maximum value from another range and vice versa.

It is to be appreciated that certain features are, for clarity,described herein in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any subcombination.

1. A compound having Formula I:

wherein: R¹, and R³ through R⁵ are the same or different at eachoccurrence and are independently selected from the group consisting ofhydrogen, alkyl, aryl, halogen, hydroxyl, aryloxy, alkoxy, alkenyl,alkynyl, amino, alkylthio, phosphino, silyl, —COR, —COOR, —PO₃R₂,—OPO₃R₂, and CN; R⁶ is selected from the group consisting of hydrogen,alkyl, aryl, alkylaryl, and arylalkyl; R is the same or different ateach occurrence and is independently selected from the group consistingof hydrogen, alkyl, aryl, alkenyl, and alkynyl; and n is an integer from0-3; and R² is aryl.
 2. The compound of claim 1, wherein R⁶ is selectedfrom the group consisting of alkyl and aryl.
 3. The compound of claim 2,wherein R⁶ is aryl.
 4. The compound of claim 3, wherein R⁶ is selectedfrom phenyl and naphthyl.
 5. The compound of claim 1, wherein R⁶ isselected from arylalkyl, alkyl, and branched alkyl.
 6. The compound ofclaim 1, wherein R² is selected from phenyl and naphthyl.
 7. Thecompound of claim 1, wherein R¹, R³, R⁴, and R⁵ are all hydrogen.
 8. Thecompound of claim 1, wherein R¹, R³, R⁴, and R⁵ are independentlyselected from hydrogen, alkyl, alkoxy, and aryl.
 9. The compound ofclaim 1, wherein n is 0 or
 1. 10. The compound of claim 1, selected fromthe group consisting of Compound H1 through H5:


11. A photoactive layer comprising a compound of claim 1 and anelectroluminescent material.